Doing a bit of post-surfing, it's a Shetland tup you've got, yes? If you stick with Shetland ewes, or other similar northern-shortailed primitive types, you would probably get away with running the tup with them from spring until early September. But you'd need to keep him separate for nearly half the year, I'm afraid.
I used to keep my Shetland tup with the flock (a breeding flock, primitives and hill types) year round, and I never had anyone tupped before mid-Oct, but that was in the uplands of the far north of England. Lower down could have been a different story.
If the ewes have any continental - Charolais for one - or Downs blood in them, they could cycle earlier, so you'd probably only get three or possibly four months when they could be together. And if there is any Dorset blood in them, you would not be able to run him with them safely ever; they will cycle any time.